The present invention relates to gallium-copper (Ga-Cu) alloy which exhibits a liquid phase at the normal temperature and to an exchangeable electrode for an evaporation system in which the Ga-Cu alloy is used.
A conventional electron microscope is disclosed in the following literatures (1) and (2).
(1) "Transmission Electron Microscopy of Metals", FIG. 59 on page 103, by Gareth Thomas, published by John Wiley & Sons, Inc. in 1962. PA1 (2) "Theories and Applications of Electron Microscope--I. Fundamental Theories and Manipulation of Electron Microscope" edited by The Society of Electron Microscope of Japan and published by Maruzen Company on Sept. 25, 1964.
In an electron microscope, the following method has been employed for the purpose of a rapid exchange of observing samples. A preevacuation chamber is provided in association with a high vacuum chamber. In advance of exchanging specimens, a specimen is placed in the preevacuation chamber and then the preevacuation chamber is preevacuated by a rotary pump or the like. When a specimen is exchanged with a new specimen, the new specimen already placed in the preevacuation chamber is transported to the high vacuum chamber so that the new specimen is placed therein in lieu of the old specimen.
If the above-mentioned microscopic method of exchanging observing specimens can be applied for an evaporation system, an evaporation sample, i.e., an evaporation source material could be exchanged with a new source material, without deteriorating an atmosphere within the vacuum chamber of the evaporation system. As a result, it is estimated that an exhausting time of the vacuum chamber is remarkably reduced and further that the reproducibility of evaporation is also considerably improved, since the condition of residual gases, i.e. background atmosphere, within the vaccum chamber is stable.
In the case of an evaporation system, however, the evaporation of the source material by feeding a large current into the source material is required in addition to the mere replacement or exchange of evaporation source material. For example, the current fed into a conventional boat type evaporation source ranges usually from 100 to 200 A. This needs a strong and tight contact of the evaporation source material with electrodes fixed within the vacuum chamber in order to ensure a stable feeding of a large current.
In this respect, if the sample exchange method used in the case of an electron microscope is applied to the evaporation system, one encounters a difficulty in removing the evaporation source in strong contact with the fixed electrode from the vacuum chamber or in placing a new source material into the vacuum chamber to in turn make it firmly contact the fixed electrode, through a manual operation from outside. With this in view, it is usual in the case of an evaporation system that the vacuum chamber is opened to allow air to be introduced into the vacuum chamber and that the old source material is removed directly by hand and then a new source material is fixed onto the electrode, for example, by screwing the source material to the electrode by hand, at every time that the exchange of source material is required. This conventional vacuum evaporation system is disclosed in "Vacuum Deposition of Thin Films", FIG. 1.2 on page 8; by L. Holland, F. Inst. P. published in 1960, or in "THIN FILM PHENOMENA", FIGS. 11 and 12 on pages 57 and 58; by Kasturi L. Chopra published by McGraw-Hill Book Company in 1969.